1. Field of the Invention
The present invention relates to digital processors, and, more particularly, to digital processors having a reduced instruction set for use in digital filter technology and the like.
2. Description of the Related Art
Digital signal processing systems usually contain a processor, which is the nerve center of the system and processes the data loaded into it in accordance with a program sequence that depends on the task to be performed, with the possibilities provided by the circuit elements having to be taken into account. The respective program sequence is either hard-wired or stored as an instruction set in a program memory, a combination of the two possibilities being generally most effective. The program memory itself may be a read-only memory ("ROM"), a random-access memory ("RAM"), or a combination of the two. If the processor is produced in large numbers, the fixed program and the fixed constants or coefficients will mostly be contained in the ROM, while the associated variable data will be stored in the RAM.
Actual signal processing takes place in the arithmetic logic unit ("ALU"), which generally contains an adder or accumulator, a multiplier, and some logic elements, such as a shifting device The central control unit is in most cases the program memory, which initiates the individual control operations required to perform the functions specified, e.g., movements of data within the arithmetic unit or between the latter and the addressable memory locations. The stored program contains the various control instructions or initiates their execution. The sequence of operations is controlled by the program counter.
Commercially available processors generally include large numbers of different instructions which can be combined into program sequences to ensure as universal applicability as possible Where universal applicability is not important, the processor can be made much smaller.